1. Field of the Invention
The invention relates to a video mixer in which a video component of the video signal to be mixed and a mixing type are preselectable for performing a mixing operation on said video signal applied to the mixer.
2. Description of the Related Art
Such video mixers provide the possibility of selecting at least one component of the video signal for performing a mixing operation, this component being subsequently subjected to the mixing operation. For example, the foreground signal, background signal or chromakey of the video signal may be selected. After the video signal has been supplied, a mixing operation, whose type is also preselectable, is then performed on the selected signal(s) of this video signal.
It is an object of the invention to improve a mixer of this type to such an extent that an additional function by means of the mixer is controllable, which function can be performed temporally parallel to the actual mixing operation performed by the mixer.
According to the invention, this object is achieved in that an additional external function is selectable at the video mixer, this additional function being selectable from predetermined additional external functions, and in that the video mixer generates a control signal during a mixing operation for controlling a selected external function, this control signal changing from a first extreme value to a second extreme value in the course of the mixing operation and serving for controlling the selected external function, an initial value of a variation of the external function being assigned to the first extreme value of the control signal and a final value of the variation of the external function being assigned to the second extreme value of the control signal.
At least one function is selectable from a list of predetermined additional external functions. This additional external function can be selected before performing a mixing operation so that it is subsequently also performed during the mixing operation.
This control is realized by means of a control signal generated by the mixer for triggering and controlling the selected additional external function. Depending on the type of the selected additional external function, the control signal is generated in an appropriate or adapted manner.
During the mixing operation, the control signal runs through signal values between a first extreme value and a second extreme value. An initial value of the variable external function is assigned to the first extreme value and a final value of this variable is assigned to the second extreme value. This provides the possibility of performing a continuous variation of the external function between the initial value and the final value in dependence upon the control signal value which changes between the two extreme values. In this way, continuous external functions can be controlled.
Moreover, it is achieved that the external function is performed in time synchronism with the mixing operation and that the variation of the external function ranges between a desired initial value and a final value. Triggering and control of the external function does not require any further operating steps, except the previous selection.
In a feature of the invention, the external function is generally selected and performed in addition to a mixing function. However, it is alternatively possible, to perform only the external function, i.e) without having preselected a video signal component, on which a mixing operation was performed.
In a further embodiment of the invention, the external function is advantageously varied proportionally to the changing value of the control signal so that also the range of variation of the external function can be influenced by the control signal. This may be used, for example, for a picture fading operation to be performed as an additional external function by the mixer, together with a synchronous sound-fading operation. Also, for example, a given audio clip could be played time-synchronously during the mixing operation.
In accordance with a further embodiment of the invention, the control signal advantageously controls an external apparatus which performs the additional external function in dependence upon the control signal.
In any case, the invention ensures that the desired external function is performed at the desired instant and is synchronized with the mixing operation and the desired course of the operation.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.